This invention relates to a back-electromotive force protection circuit. More particularly, it relates to a back-electromotive force protection circuit in which the circuit is protected against the back-electromotive force generated during startup or halting of a hard disc provided on a personal computer or an engineering work station.
Recently, as the computer processing capability is improved. the amount of handled data is increased drastically. On the other hand, as the application software is diversified and improved in the functions of the application software, the scale of the application itself is increased. As an example, in a certain software, such as a word processor, as a type of the application, the size of the application exceeding 200 MB is not uncommon.
As a device for storing the large-scale application or a large amount of data, hard discs are routinely used in order to cope with demands in readout and writing speeds.
FIG. 2 shows connection of a conventional hard disc.
In FIG. 2, 50 is a power source, and 52 a hard disc. The hard disc 52 has its positive side terminal connected to a positive side terminal of a power source 50 via a connection line 56, while having its negative side terminal connected to a negative side terminal of the power source 50 via a connection line 58.
In the figure 54 is a load connected across the connection lines 56 and 58. The load 54 is, for example, a control circuit for the hard disc 52. This load 54 and the hard disc 52 are actuated by the power supplied via the connection lines 56, 58.
However, the following problems have been encountered in the course of investigations toward the present invention.
In the conventional device, shown in FIG. 2, there lacks a circuit for protecting the load 54 from a back-electromotive force BV generated upon startup or halting of the hard disc 52, such that, if the hard disc 52 generates the back-electromotive force, there is the possibility that the back-electromotive force be applied to components other than the hard disc 52, such as load 54, thus deteriorating the electrical performance or disabling the intended operation of these components.
The same problems would arise for any driving mechanism or unit driven by the power source, e.g., CD drive etc.
In view of the above-described status of the art, it is an object of the present invention to provide a back-electromotive force protection circuit that is capable of protecting circuit components against the back-electromotive force produced in the hard disc or in general a power-driven unit.
It is another object of the present invention, to provide a protection circuit against back-electromotive force with a simplified structure.
Other objects will become apparent in the entire disclosure.
According to one aspect of the present invent ion, there is provided a back-electromotive force protect ion circuit. The protect circuit is characterized by a power source, a hard disc (or power-driven unit) having a positive side terminal connected via a first connection line to the positive side terminal of the power source and having a negative side terminal connected via a second connection line to the negative side terminal of the power source, a load provided between the first connection line and the second connection line and line breaking means or element which turns off the second connection line if no power is supplied from the power source.
The present invention is also characterized in that there is provided a resistor which consumes the back-electromotive force generated from the hard disc between the line breaking means and the hard disc.
The present invention is also characterized in that line breaking means is a FET having its gate connected to the first connection line.
Other features or aspects of the present invention are also mentioned in the appended claims which disclosure is herein incorporated by reference thereto.